Conventionally in cases such as a case where an interlace image is converted into a progressive image, a case where an image is enlarged, and a case where the resolution of an image is enhanced, various methods of interpolating an image have been proposed using pixel data on adjacent original pixels (corresponding to the amount of data representing luminance on a display).
Typical examples of an image interpolating method are a simple interpolating method and a linear interpolating method. The simple interpolating method is a method of giving pixel data on either one of pixels adjacent to a pixel to be interpolated on the upper and lower sides (or on the right and left sides) to the pixel to be interpolated as pixel data. The linear interpolating method is a method of giving the average of pixel data on pixels adjacent to a pixel to be interpolated on the upper and lower sides (on the right and left sides) to the pixel to be interpolated as pixel data.
In the simple interpolating method, however, the pixel data on the pixel adjacent to the pixel to be interpolated is given as it is. When there is a diagonal edge portion in an image reproduced on a display or the like, backlash occurs in the edge portion. On the other hand, in the linear interpolating method, the average of the pixel data on the pixels adjacent to the pixel to be interpolated on the upper and lower sides (on the right and left sides) is given. Accordingly, the vicinity of the pixel to be interpolated is an edge portion. When the difference between the pixel data on the pixels adjacent to the pixel to be interpolated on the upper and lower sides (on the right and left sides) is large, the interpolated pixel takes an intermediate value, so that the edge portion is blurred.
The present invention provides an image interpolating method capable of preventing backlash and blur from occurring in an edge portion in interpolating an image as well as capable of reproducing a smooth image.